Hypothetical Zeolitic Frameworks: In Search of Potential Heterogeneous Catalysts

Hypothetical zeolitic structures were systematically enumerated using tiling theory and then characterized
with a view to finding those that are chemically feasible. The energy of each framework, treated as a polymorph
of silica, was first minimized using computational chemistry methods. Optimized structural parameters,
framework energy relative to α-quartz, framework density, and internal volume accessible to sorption of
small molecules were then calculated for each structure. Chemical feasibility was evaluated by means of a
“feasibility factor” derived from the correlation between lattice energy and framework density. Finally, the
structures most suitable for potential applications in heterogeneous catalysis and sorption (those with wide
channels and/or cavities that are accessible to external molecules) were identified. Very few structures with
one or two crystallographically distinct sites for silicon (“uninodal” and “binodal”) were found to be promising
in this respect. In contrast, there are 100 trinodal structures that are potentially suitable for practical applications.
These are described and discussed.